In the practice of diagnostic medicine it is often necessary or desirable to perform a biopsy, or to sample selected tissue from a living patient for medical evaluation. Cytological and histological studies of the biopsy sample can then be performed as an aid to the diagnosis and treatment of disease. For example, biopsies can be particularly useful in diagnosing and treating various forms of cancer, as well as other diseases in which a localized area of affected tissue can be identified.
Biopsies are routinely performed on tissue using motor driven or spring-driven biopsy devices, which employ a working needle set to engage and sever tissue at a targeted tissue site. The needle set typically includes a stylet defining a tissue piercing tip and a tissue receiving opening, and a cutting cannula adapted to cut tissue that is disposed within the tissue receiving opening. In some devices, vacuum is provided to assist in drawing tissue into, as well as maintaining said tissue, within the tissue receiving opening during a cutting operation.
During a typical biopsy procedure, the biopsy device is positioned along a predetermined path that will result in the biopsy device being operatively positioned to reach a target site for performing the biopsy. The stylet is then driven into the tissue and tissue then prolapses into the tissue opening. The cutting cannula is then advanced along the stylet, and over the tissue opening. This forward movement of the cutting cannula operates to sever the prolapsed tissue, thereby obtaining a tissue sample or core, which becomes trapped within the tissue opening of the stylet. With the cutting cannula effectively closing the tissue opening, the biopsy device is then withdrawn from the target site, carrying the sample disposed in tissue opening. To collect the biopsy sample, the cutting cannula is retracted to expose the tissue opening of the stylet, thereby permitting the biopsy sample to be removed from the biopsy device. The procedure may be repeated several times until satisfactory samples have been obtained.